[ 8 S ] 
luminous, when the Light has come dlre&ly to them, 
which will not have that Appearance when the Light 
has paffed thtough the Glais. He laftly tried what 
Light they would imbibe from very bright Flame, 
and found, that Alabafter itfelf, which is faturated 
more than any Subftance by the Sun’s Rays, imbibed 
exceedingly little. The next Query is, how long 
thcfe Bodies fhould remain in the Light to be fuf- 
ficiently faturated J Four or five Seconds were found 
the utmoft Length of Time required for that Purpofe. 
The other Query is. How long the received Light 
will continue in thefe Phofphori ? It does not lad the 
fame Time in all ; but continues more or lefs, from 
2. Seconds to 8, in proportion to the Strength of 
the Phofphoms , and the Quantity of Light received. 
We pafs now to thofe Phofphori, which are pro- 
duced by Art ; and, firft, to them which are made by 
the Maceration of Plants alone, and without any Fire ; 
fuch as Thread, Linen Cloth, but, above all. Paper. 
The luminous Appearance of this laft is greatly in- 
creafed by Heat. This is confirmed by two Experi- 
ments : The firft is, by expofing the Paper, fpread 
upon an iron Grate, to the naked Fire, yet not near 
enough to fcorch it, and then laying a warm Brick 
thereon to retain the Heat ; by which means it was 
obferved, that where the Paper was not skreened by 
the iron Grate, it was moft luminous ; fo that, by 
the Lights and Shades, you might diftinguifh in the 
dark the Image of the iron Grate a conftderable Time. 
The other Experiment is the Application of the Pa- 
per to a Plate of warmBrafs j from which, when in 
the dark, you might very eafily, by its being lefs lu- 
minous,. 
